Described below are a method for operating a combined heat and power plant and a combined heat and power plant.
Combined heat and power plants, which simultaneously provide electrical energy and heat, are becoming increasingly important for supplying energy, firstly because they typically are very efficient and hence have low consumption and emission values, and secondly because they can be used to compensate fluctuations in the feed-in of renewables.
Combined heat and power plants are usually operated either in a heat-operated or power-operated mode, depending on which demand determines the regulation of the combined heat and power plant. It is known here, in cases where there is a greater demand for electricity than for heat, to temporarily store the excess heat generated in corresponding stores so that the heat and the electricity can be utilized asynchronously. However, the typical sizes of store here enable the combined heat and power plant to operate without a thermal load for only a few hours. If, when a store is full, there is still no thermal load, then such a combined heat and power plant must, as necessary and despite the continuing demand for electricity, adjust its operating mode because of insufficient cooling. When a combined heat and power plant is used in conjunction with electricity networks with a high degree of photovoltaic generation or use of wind power, it can now be the case that particularly high electrical loads are required by the combined heat and power plant without the heat which is generated at the same time being removed. Because of the limited size of the stores, after just a few hours of rain or a few hours of no wind, failure of the combined heat and power plant may therefore occur, so that stand-by power must additionally be maintained which can be used in this eventuality.
However, this is not advisable from either an operational or economic perspective.